An aqueous blue-coloured solution of a transition metal sulphate reacts with `H_2S` I acidic medium to give a black precipitate A which is insoluble in warm auqous solution of KOH. The blue solution on treatment with KI in weakly acidic medium turns yellow and produces a white precipitate B. Identify the transition metal ion. write the chemical reactions involved in the formation of A and B.

Explanation

An aqueous blue -coloured solution of a trastion metal sulphate reacts with `H_(2)S` in acids medium to give a black precipitate A which is insoluble in warm aqueous solution of `KOH` it most be a black precipitate of CuS because copper salphate is blue coloured also .The blue solution on troatment with KI in weakly acid medium furm yellow and producess a white precipitate B in this reaction copric iodide is formed first which decomposess to give white cupose iodide iodide
`CuSO_(4) + H_(2)S overset("Acidic medium")rarr underset(Black)(CuSdarr) +H_(2)SO_(4)`
`CuSO_(4) +2KI rarr CuI_(2) +K_(2)SO_(4)`
`2CuI_(2) rarr Cu_(2)I_(2) darr +I_(2)`